Apparatus for the simultaneous collection of pore water specimens from adjacent areas of aquatic sediments

ABSTRACT

A specimen collection apparatus for the simultaneous collection of pore water from adjacent areas of aquatic sediments provided with a plurality of miniaturized tubular specimen collectors in a vertical array mounted for horizontal movement into and out of a housing relative to the sediment. A Benthin chamber may be provided spaced from the specimen collection apparatus such that the specimen collectors thereof may be moved into the sediment below the Benthin chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention, in general, relates to a novel apparatus forsimultaneously collecting specimens of pore water from adjacent areas ofaquatic sediments, and, more particularly, to an apparatus of the kindreferred to provided with a plurality of miniature specimen collectorsarrayed in a housing and provided with a hydrophillic micro-porousplastic hose connected, at its pore water intake side, to a support railand, at its pore water discharge side, to a vacuum device and a storagedevice.

2. The Prior Art

Such a specimen collection apparatus is used for simultaneouslycollecting of pore water specimens from aquatic sediments forgeochemical and bio-geochemical examinations of the transition zonebetween, or at the interface of, sediment and water. Processes in thesediments and in the bottom water generate gradients in the pore water,for instance in the concentration of its. Especially the decay oforganic substances and the dissolution of minerals generate a gradientin the pore water. Pore water is often examined ex situ by taking asediment core onboard a ship or ashore where it is divided intosub-samples. They are squeezed out under pressure and centrifuged toyield their pore water. However, such a process may change the chemistryof the pore water as a result of temperature and pressure changes aswell as of undesirable oxidation and contamination.

For that reason, in situ systems which examine the sediment in itsnatural environment are being used more and more. A so-called “wholecore squeezing” process is known from the paper “The ROLAI²D lander: Abenthic lander for the study of exchange across the sediment-waterinterface” by F. L. Sayles et al. (Deep-Sea-Research, Vol 38, No. 5, pp.505-529, 1991)’, hereafter sometimes referred to as “Publication I”,which discloses depositing on the sediment a free-falling support system(“lander”) for apparatus for examining the bottom of the sea bycapturing a sediment core in a sampling tube. The sediment is squeezedout from below and from above. The pore water escapes through openingsin the tube into collection containers. Not only is the very complicatedand complex modus operandi of the specimen collector disadvantageous,but the sediment can only be examined once since the sediment compoundis destroyed during the collection of the sediment. In view of the factthat the sediment is being compacted during its compression and is thusmoved by the openings in the specimen tube, it is at best difficult toassign the taking sites to a defined horizon (depth of sediment).

The paper “An in situ sampler for close interval pore water studies” byR. H. Hesslein (Limnology and Oceanography 21(6), Nov. 1976, pp.912-914), hereafter sometimes referred to as “Publication II”, disclosesthe so-called “peeper” method which operates on the principle ofdiffusion. The sediment receiving apparatus consists of a corpus withmany chambers which are filled with distilled water and covered my adiaphragm. The specimen collection apparatus is installed in thesediment and thereafter an equilibrium is established between the waterin the chambers and the pose water. After an equilibrium has beenestablished the specimen collection apparatus is retrieved for analyzingthe pore water within the chambers. A drawback inherent in this processmay be seen in the fact that for proper examination of the sediment thespecimen collection apparatus must remain therein for rather a longtime. Moreover, only one examination can be performed so that abruptparameter changes in the sediment cannot be detected. Furthermore, thereremains the risk of the equilibrium not having been established when thespecimen collector is being retrieved.

A third in situ process has been disclosed by the paper “A new devicefor in-situ-pore-water sampling” by A. Bertolin et al. (Marine Chemistry49 (1995), 233-239), hereafter referred to from time to time as“Publication III”, and involves a suction specimen collector. Thespecimen collection device consists of a blade-like housing the narrowfront surface of which defines its size and which is usually equippedwith openings protected by filters or gauze through which pore water issucked into storage containers provided behind the openings, uponapplication of vacuum pressure. One disadvantage of this process is thevery long adaptation time of about two weeks the specimen collectorrequires after being placed in the sediment before the sediment can beexamined. Furthermore, the pore water is sucked in through relativelylarge opening surfaces so that the possible vertical and lateralresolution are rather poor. Also, the quantity of pore water which canbe taken in is quite limited in cases where it is to be taken in free ofany contamination.

Every one of the mentioned three apparatus for in situ processingsuffers from the fact that they disturb or destroy the surface of thesediment when they penetrate into it. The result will thus beundesirable artificial mixing zones, and the simultaneous use of aso-called “Benthin chamber” is rendered impossible. A Benthin chamber isa cylindrical chamber without a bottom which is placed on the sediment.Any change in the concentration of substances in the volume of waterincubated within the chamber yields an indication about any exchange orinteraction about the interface of sediment and water. By rotating thelid of the Benthin chamber or a stirrer within the chamber below its lida three-dimensional current can be generated in the interior of thechamber which will also flow through areas of the sediment. Thisarrangement is based upon the recognition that advective currentsgreatly affect the movement of dissolved and particulate matter at thebottom of the sea. A Benthin chamber is a suitable apparatus forconducting experimental studies of such movements.

An article “Pore water sampling with Rhizon sampler” by M. Koelling,hereafter sometimes referred to as “Publication IV”, has been publishedby the University of Bremen, Germany, and may be down-loaded athttp://www.geochemie.uni-bremen.de/koelling/rhizon p.html (status 20October 2004) and relates to the use of miniaturized specimen collectorswith a hydrophillic micro-porous plastic hose which at its pore waterintake side is connected to a support rail and with a vacuum removaldevice at its pore water discharge side. This so-called Rhizon bottommoisture specimen collector is a miniaturized filter tube with amicro-porous polymeric hose at its intake side and a vacuum-pressureproof PVC hose at its discharge side and which represents an artificialroot developed for collecting bottom moisture in unsaturated bottomzones (see Prospectus P2.30 of the Eijkelkamp company “Soil MoistureSampling” pp. 183-186 which may be down-loaded athttp//:www.waterland.com.cn/PDF/P2-30e.pdf, status 20 October 2004 andProspectus Doc. No. 1190 “Techinfo Ben Meadows Company: Rhizon SoilMoisture Sampler”, 2002 Lab Safety Supply Inc.).

According to Publication IV by the University of Bremen, the specimencollector described is used in a specimen collection apparatus forsimultaneously collecting pore water from adjacent aquatic sedimentareas for the ex-situ examination of water-saturated marine sediment.Hence, the known filter tubes may be said in some ways to be misused.The sediment to be examined is initially gathered in a tubular housingwhich is then moved ashore and closed by a lid. In the wall of thehousing there is provided a series of small bores disposed parallel tothe longitudinal axis of the housing through which the supported plastichoses may be injected into the sediment. The specimen collectors arethus arranged in a row and each individual pore water specimen gatheredin a storage tube either by way of a small connected vacuum pressuretube or by way of an injection syringe functioning as a suction device,can be assigned to an area of the sediment. Publication IV does not,however, disclose whether the sediment area extends vertically oflaterally relative to the bottom of the body of water. A disadvantage ofthis known specimen collecting apparatus is that it is designed for exsitu pore water examination and that the injection of the tubularhousing into the area of sediment to be examined results in asubstantial disturbance of the natural ambient conditions. The ex situmeasuring process and the disturbance or destruction of the sedimentsurface preclude any measurements accompanying the specimen collection,for instance by a Benthin chamber.

OBJECTS OF THE INVENTION

Proceeding upon the apparatus known from Publication IV, it is an objectof the instant invention so to improve a specimen collecting apparatuswith miniaturized specimen collectors that it can perform in situexaminations of aquatic sediments in vertical high-resolution.

Another object resides in the provision of an apparatus of the kindreferred to which is capable of performing examinations withoutdisturbing the surface of the sediment to allow in situ accompanyingexaminations.

SUMMARY OF THE INVENTION

In the accomplishment of the aforesaid objects the invention providesfor a specimen collection apparatus for simultaneously collecting porewater from a plurality of adjacent aquatic areas of sediment andprovided with a plurality of miniaturized specimen collectors arrayedwithin a housing with a hydrophillic micro-porous plastic hose providedat the pore water intake side thereof with a support rail and at thepore water discharge side thereof with a suction removal device and astorage device, the specimen collectors being vertically disposed in asupport device within a narrow side of a blade-like housing andconnected to a process unit in which the specimen collectors by theintake side thereof may be moved into and out of the sediment areasrelative to the housing in the area of the narrow side thereof.

Other object will in part be obvious and will in part appearhereinafter.

An advantageous application of the specimen collection apparatus of theinvention relates to an in situ interaction with a Benthin chamberplaced upon the bottom of the body of water at a distance from thespecimen collection apparatus sufficient to allow movement of thespecimen collectors into the sediment area below the Benthin chamberwithout disturbing the sediment surface within the Benthin chamber.

The specimen collection apparatus in accordance with the invention isprovided with a number of sample collectors structured as miniaturizedfilter tubes of the kind referred to above disposed vertically within asupport device in a blade-like housing. The support device is arrangedwithin a housing which extends downwardly in a conical pointedconfiguration. The blade-like configuration allows the housing simply topenetrate in a vertical direction into the surface of the sedimentwithout significantly damaging the surface of the sediment. Once thehousing has reached its vertical depth of penetration—which is usuallywithin the upper several decimeters of the layer of sediment—theindividual specimen collectors disposed vertically of each other withinthe sediment and thus make possible high-resolution vertical profilemeasurements, may be actuated. For this purpose they are horizontallyinjected by their supported intake sides from the narrow front surfaceof the blade-like housing into the sediment area adjacent the housing.Thus, the examination is not performed within the housing, but ratherwithin an undisturbed neighboring area which as a result of the smalldiameter of the protruding specimen collectors is not unduly disturbed.Taking a specimen does not require a long dwell time. Directly thespecimen collectors have been injected into the sediment the examinationmay commence. Several specimens may be collected from the same sedimentarea by actuating the suction removal device at predetermined intervalsof time. The pore water specimens may be mixed or stored separately inappropriate storage devices. Multiple actuation may also take place byrepeated injection and withdrawal of the specimen collectors so that thechronologically observable conditions within the sediment may adjustthemselves without disturbance by the specimen collectors,

In summary, the specimen collection apparatus makes possible thecollection, under in situ conditions, of pore water specimens fromdifferent levels or horizons in the upper decimeters of an undisturbedaquatic sediment. It allows an examination of pore water within thesediment in a vertical high-resolution which may take place once orrepeatedly at predetermined intervals of time in order to allow forexamination of chronological changes. The pore water profiles providedby the specimen collection apparatus may provide new insight into themotion an reaction processes within the sediment and at the interface ofsediment and water. For examining the interaction at this interface, theuse of the claimed specimen collection apparatus makes it possible toapply a Benthin chamber. Hitherto it has not been possible directly toexamine the pore water below such a chamber. By laterally ejecting thespecimen collectors from the blade-like housing of the specimencollection apparatus it has, however, become possible in view of thefact that the sediment surface disposed immediately above the specimencollector is not disturbed or damaged by the specimen collectingapparatus. In this fashion, it is possible to conduct furtherexaminations in this area. Accordingly, the specimen collectingapparatus combines high functionality in keeping with theoreticaldemands for a high-quality examination of pore water by an anoxicexamination, a low dead volume in the apparatus and, by the fact thatthe pore water is collected in a filtered state because of the specimencollectors structured as miniaturized filter tubes with a micro-porousplastic hose for taking in pore water, with a high suitability for usein the field because of the low disturbance of the sediment to beexamined.

The basic components of the in situ specimen collection apparatus arespecimen collectors structured as rhizons. Rhizons are commerciallyavailable soil moisture specimen collectors. At their pore water intakeside they usually consist of a piece of hydrophillic micro-porouspolymeric hose glued to a support rail which may be a stainless steelwire or plastic. Their discharge side is connected to a PVC hose bymeans of which a pore water sample may be sucked by vacuum pressure intoa storage device. In the simplest case, the storage device may bestructured as small tubes; but multiple-chamber storage containers maybe used as well. An unequivocal association of each separate storagecontainer with its specimen collector is important for establishing acorrect profile curve of every parameter. The suction device may bemanually operable injection syringes or motor-driven peristaltic pumps.Each specimen collector may be associated with its own separatelyactuable suction element. Alternatively, the specimen collectors mayshare a common suction device. Manual operation as well as motorized andautomatic actuation of the section device are possible.

The specimen collectors are mounted into a support device such that theymay be mechanically moved into the sediment once the blade-like housinghas been pressed into the sediment. A distinction may be made betweentwo variants: First, each specimen collector is separately supported andmay be separately pushed into the sediment or, second, all samplecollectors are mounted in a common support device and are pushed intothe sediment together. In the first case, the support for each specimencollector is provided with a support element for each specimencollector, and for each support element there is provided a separatelyactuable movement element in the movement device. Each support elementmay be structured as a tube which is rigidly connected to the supportdevice and which receives the specimen collector in its withdrawn state.Hence, the tube function as protective tubes for the specimen collectorsin their withdrawn state. The specimen collectors are supported byangular rails such that by moving the angular rails they may be moved asa component of the movement element out of the forward end of the tubes.For forward and reverse movement each movement element may be providedwith a bidirectional cable drive. These may be some kind of a “fishingline” attached by bores at the forward and rear ends of a tube on theangular rail of each specimen collector. By pulling the correspondingend of the fishing line (or of separate fishing lines) and the ensuingmovement of the angular rail the specimen collector may be pushed intoor pulled out of the sediment. Each specimen collector may be actuatedseparately. However, all cable drives may alternatively be guided by acommon support block so that, in the manner of a puppet control, thatmay be actuated at the same time.

In the second case of a common support, the support device is rigidlyconnected to all specimen collectors, with the specimen collectorsextending out of the support device by their intake sides, and isstructured so as to be movable. In this embodiment, too, a bidirectionalcable drive may be used. It would engage the forward and rear ends ofthe support device and by actuation of the appropriate cable it may moveout of and into the support device. It is also possible to providemotorized as well as automatic movement by separate or common drives.

DESCRIPTION OF THE SEVERAL DRAWINGS.

The novel features which are considered to be characteristic of theinvention are set forth with particularity in the appended claims. Theinvention itself, however, in respect of its structure, construction andlay-out as well as its manufacturing techniques, together with otheradvantages and objects thereof, will be best understood from thefollowing description of preferred embodiments when read in connectionwith the appended drawings, in which:

FIG. 1A is a side elevation in cross-section of the specimen collectionapparatus in accordance with the invention;

FIG. 1B is a frontal view of the specimen collection apparatus of FIG.1A;

FIG. 2 is a detailed view of a specimen collection apparatus inaccordance with the prior art; and

FIG. 3 is a measuring diagram of two parameters recorded with thespecimen collection apparatus in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

FIG. 1A depicts in side elevational cross-section a specimen collectionapparatus PNG for the simultaneous collection of pore water PW fromadjacent aquatic sediment areas SB during its used on the bottom of anocean. The specimen collection apparatus PNG is provided with asubstantially closed housing SG the downwardly tapered blade-likeconfiguration and weight of which facilitate a substantially verticaland stable penetration of the specimen collection apparatus PNG into thesediment area SB. The frontal view of FIG. 1 B of the specimencollection apparatus PNG clearly depicts the blade-like configuration ofthe housing SG. In a small forward side SSS of the housing SG sixspecimen collectors PN are horizontally arranged within a support deviceTE. The vertically stacked arrangement of the specimen collectors PNmakes it possible to determine a vertical measuring profile ofpredetermined parameters in the sediment area SB. For this purpose, thespecimen collectors PN may by their intake side ANS be horizontallymoved into and out of the sediment areas SB by the narrow forwardsurface SSS of the blade-like housing SG.

In the embodiment shown in FIG. 1A each specimen collector PN is movablymounted in a tube RO or support element TEL of its own which is rigidlyconnected to a support device TE. The figure shows the intake sides ANSof the specimen collectors PN supported by support rails SS in theirposition extended into the sediment areas SB. This is accomplished by amovement device VE constructed of individual movement elements VEL of anumber equal to that of the number of tubes. In the selected embodimentthe movement element VEL is a manually or motor (also automatically)driven bidirectional cable drive NSZ which is connected to the forwardand rear ends of an angular rail WS rigidly connected to the specimencollector PN. By actuation of the appropriate end of the cable drive BSZthe specimen collector PN is pushed out of the protective tube RO i.e.the support element TEL, so that its intake side ANS penetrates into thesediment areas SB, or withdrawn from it.

In another embodiment not shown in FIG. 1A all specimen collectors PNare rigidly connected to the support device TE. This may be a simpleperforated piece of sheet metal and a central support rod. All specimencollectors PN extend over the support device TE by their intake sidesANS. By moving the entire support device TE the intake sides ANS of thespecimen collectors PN may be moved into and out of the sediment areasSB. The movement device VE may again be actuated manually or by a motor(also automatically), for instance by a single bidirectional cable driveBSZ which engages the support device TE.

In addition to the specimen collection apparatus PNG FIG. 1A depicts aBenthin chamber BK placed upon the bottom of the body of water. Since ithas no bottom, it penetrates into the sediment area SB. By a stirrerRUH, a circulating current affecting the exchange or interactiveprocesses in the sediment area SB. These may be detected by the specimencollecting apparatus PNG by the specimen collectors PN in theirlaterally expended state examining the sediment area SB below thenBenthin chamber BK without damaging or destroying the bottom of thewater GB within the Benthin chamber BK and affecting the interactive orexchange processes at the interface between the water and the sediment.Additional water specimens WP for comparative measurements may beobtained in the Benthin chamber BK by way of collective lines SA.

The specimen collectors PN used are miniaturized filter tubes, so-called“Rhizon bottom moisture specimen collectors”, see FIG. 2. They arecommercially available, but in the specimen collecting apparatus PNG inaccordance with the invention they are not being used in connection withunsaturated bottoms but, rather, with bottoms saturated by water. Inaccordance with FIG. 2 a specimen collector PN in accordance with theprior art at its pore water intake side ANS consists of a hydrophillicmicro-porous plastic or polymeric hose KS of a length of, for instance,5 or 10 cm and a diameter of 2.2 mm with a pore size of 0.2 μmstabilized by a supportive rail SS. This may be metallic or plasticstiffening wire. At its pore water PW discharge side ABS the specimencollector is provided with a PVC hose PVCS by which it is connected, byway of a connector VB with an injection syringe IS functioning as asuction removal device ASV with an inter=grated storage device LV. Bymeans of connecting hoses VSS made of silicon extension hoses VLS may beconnected to the PVC hose PVCS.

FIG. 3 by way of example depicts two chloride profiles (chloride inmmol/l above the sediment depth in cm) and two silicate profiles(silicic acid in μmol/l above the sediment depth in cm) which resultedfrom measurements made by the stationary specimen collection apparatusPNG at the same location in a sediment area SB on the bottom of a bodyof water GB at times A and B. The chronological changes which may beconsidered to result from interactive or exchange processes may beclearly seen in the curves.

1. A specimen collection apparatus for simultaneously collecting porewater from adjacent aquatic sediment areas, comprising: a plurality ofminiaturized specimen collectors comprising a hydrophillic micro-porousplastic hose having means comprising a pore water intake side and a porewater discharge side; a support rail at the pore water intake side; asuction device and a storage device connected therewith at the porewater discharge side; a housing of substantially blade-like structurewith a vertical narrow surface and provided with a support device forreceiving the specimen collectors with their pore water intake side inalignment with the narrow surface; and means for horizontally moving thespecimen collectors relative to the sediment areas between a positionout of and a position within the blade-like housing.
 2. The apparatus ofclaim 1, wherein the support device is provided with a support elementfor each specimen collector and wherein each specimen collector isprovided with its own means for moving.
 3. The apparatus of claim 2,wherein each support element is structured as a tube rigidly connectedto the support device and wherein the tube receives the specimencollector in its position within the housing and wherein each means formoving comprises an angular rail rigidly connected to the specimencollector and a cable drive.
 4. The apparatus of claim 1, wherein thesupport device is rigidly connected to and moveable with every specimencollector.
 5. The apparatus of claim 4, wherein the means for moving isprovided with a bidirectional cable drive.
 6. The apparatus of claim 1,wherein the support device comprises a support wire made of one ofstainless steel and plastic.
 7. The apparatus of claim 1, wherein thesuction device of each specimen collector comprises a separate suctionelement.
 8. The apparatus of claim 1, wherein the suction device isassociated with every specimen collector in common.
 9. The apparatus ofclaim 1, wherein the specimen collectors are structured as Rhizon bottommoisture specimen collectors.
 10. A method of using an apparatus ofclaim 9 comprising the step of positioning a Benthin chamber at adistance from the specimen collection apparatus such that the specimencollectors may be moved into the sediment area below the Benthinchamber.